For a number of advisors, even the mention of "therapy" or "therapeutic" evokes a negative reaction. This resistance is often due to concern that they might do or say something wrong to a client who is venting strong feelings.
Reflecting clients' thoughts and feelings back to them with empathy and compassion is good, deep listening, not therapy, and cannot harm them. If the intensity of feelings being directed at you ever makes you feel that you're in over your head, it's time to consider referring the client to a therapy professional.
Another sign of being outside your zone is obsessing about particular clients. Thinking about them on weekends, worrying about them, and feeling overly responsible for them are all signs that you need to consult a trained professional, either for supervision or an outright referral.